article {
  padding-top: 50px;
  display: flex;
  justify-content: center;
  align-items: center;
}
article .neumorphism {
  border-radius: 25px;
  background: linear-gradient(145deg, #c4c2c2, #e9e7e7);
  box-shadow: 4px 4px 8px #929191, -4px -4px 8px #ffffff;
}
article .calculator {
  width: 250px;
  height: 500px;
  padding: 20px;
  font-size: 20px;
}
article .calculator h2 {
  text-align: center;
  margin-bottom: 20px;
}
article .calculator p {
  height: 50px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  line-height: 50px;
  padding: 0 20px;
  margin-bottom: 20px;
}
article .calculator .input-group input {
  font-size: 20px;
  height: 50px;
  width: 100%;
  margin-bottom: 15px;
  padding-right: 20px;
  text-align: right;
  border: 0;
}
article .calculator .btn-group {
  display: flex;
  flex-wrap: wrap;
}
article .calculator .btn-group button {
  flex: 1 0;
  min-width: 78px;
  min-height: 78px;
  margin: 5px;
  border: 0;
  font-size: 50px;
}
